detect host suspend

To detect a host suspend event, you can listen for the ACPI (Advanced Configuration and Power Interface) events that are generated when the system enters a suspended state.

On Windows, you can use the Power Management APIs to register for power management events, including suspend and resume events. You can use the `SetPowerSettingNotification` function to register for the `GUID_SESSION_DISPLAY_STATUS` power setting, which indicates changes in the session display status, including when the system is suspended.

On Linux, you can use the `systemd-logind` service to receive notifications of system suspend and resume events. You can use the `sd_event_add_signal` function to register for the `SIGUSR1` signal, which is sent by `systemd-logind` when the system is suspended.

Once you receive a notification of a suspend event, you can take appropriate actions such as saving data, closing connections, or shutting down services gracefully.